MESO: Mesoscale Discussion 1703

ACUS11 KWNS 042323
SWOMCD
SPC MCD 042323
OHZ000-MIZ000-INZ000-050130-

MESOSCALE DISCUSSION 1703
NWS STORM PREDICTION CENTER NORMAN OK
0623 PM CDT SAT AUG 04 2012

AREAS AFFECTED...PORTIONS CENTRAL/NRN INDIANA...SRN LOWER
MI...LE...WRN/NRN OH.

CONCERNING...SEVERE THUNDERSTORM WATCH 559...

VALID 042323Z - 050130Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 559
CONTINUES.

SUMMARY...WW MAY BE CLEARED BEHIND MAIN MCS THAT WAS MOVING EWD
40-45 KT ACROSS SWRN LOWER MI AND NRN INDIANA AS OF 23Z. ADDITIONAL
WW AND/OR COUNTY EXTENSIONS OF WW 559 MAY BE REQUIRED E OF PRESENT
CONFIGURATION.

DISCUSSION...MAIN MCS IS SUPPORTED BY STG LOW-LEVEL COLD POOL WITH
2-4 MB PER 2 HR ISALLOBARS IMMEDIATELY BEHIND MAIN PRECIP
AREA...THEN WAKE DEPRESSION OF SIMILAR NEGATIVE MAGNITUDES.
THERMODYNAMIC ANALYSES AND MODIFIED FCST SOUNDINGS SUGGEST PATCHY
BUT MOSTLY FAVORABLE SUPPORT ACROSS REMAINDER SRN LOWER MI...NERN
INDIANA ND NWRN OH. SRN PORTION OF COMPLEX IS OVERTAKING
ADDITIONAL/RELATIVELY DISCRETE CONVECTIVE ELEMENTS FORMING IN WARM
SECTOR...WHERE 2000-3000 J/KG MLCAPE IS EVIDENT. AS THIS PART OF
COMPLEX ENTERS OH...IT WILL MOVE INTO AREAS AT LEAST TEMPORARILY
STABILIZED BY SECONDARY TSTM BAND DESCRIBED BELOW.
HOWEVER...MOIST/SSWLY-SWLY FLOW FROM SFC TO 850 MB WILL SUPPORT AIR
MASS RECOVERY INTO NWRN OH. CORRIDOR OF ENHANCED MIDLEVEL FLOW --
RELATED TO MCV OVER SRN WI -- IS ENHANCING DEEP SHEAR ACROSS NRN
INDIANA AND SERN LOWER MI...WITH WSWLY EFFECTIVE SHEAR VECTORS OF
30-40 KT.

MIXED SIGNALS LEND UNCERTAINTY TO MAINTENANCE OF THAT PART OF MCS
OVER EXTREME NRN INDIANA AND SRN LOWER MI...BUT ANOTHER WW STILL MAY
BE NEEDED FARTHER E TOWARD SERN LOWER MI. HIGH THETAE ALSO IS
EVIDENT ACROSS SRN LOWER MI...WITH 70S F SFC DEW POINTS AND 1.5-1.75
INCH PW. NRN PORTION OF MCS WILL INTERACT WITH WEAKER/NON-SVR NWRN
EXTENSION OF OH CONVECTION BEFORE ENCOUNTERING THAT AIR
MASS...THOUGH STRENGTH OF COLD POOL MAY BE MAINTAINED THROUGH
RELATIVELY STABLE CORRIDOR JUST E OF MI SEGMENT OF MAIN MCS.

SECONDARY BAND OF STG-SVR TSTMS WILL MOVE ENEWD ACROSS PORTIONS NRN
ON IN REGIME OF FAVORABLE BUOYANCY AND WEAK CINH FOR A FEW MORE
HOURS...BUT MODEST DEEP-LAYER FLOW AND SHEAR. FCST SOUNDINGS
SUGGEST 70S F SFC DEW POINTS WILL SUPPRESS RATE OF DIABATIC SFC
COOLING AND HELP TO MAINTAIN 1500-3000 J/KG MLCAPE THROUGH AT LEAST
02Z. THEREAFTER...STABILIZATION WILL BE GRADUAL...WHILE LEADING
EDGE OF ACTIVITY CONTINUES TO LIFT PARCELS VIA FORCED ASCENT. MAIN
CONCERN WILL BE DAMAGING GUSTS.

..EDWARDS.. 08/04/2012

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...PBZ...CLE...ILN...DTX...IWX...GRR...IND...

LAT...LON 39838399 40368626 41038613 42028602 42598678 43148248
42838246 42538259 42618264 42698267 42648281 42538284
42408288 42328302 42168313 41998315 41828339 41718344
41528287 41388246 41508198 41718129 40508152 40108195
39788391 39838399

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